1. Field of the Invention
The present invention relates to a coil device, and specifically relates to a coil device capable of performing wire connection in a firm and secure manner.
2. Description of the Related Art
A drum core and a terminal shape as shown in a publication (WO2009/034860), for example, are well known for thinning. In the coil device shown in the publication, however, lead parts of a wire for winding are soldered with terminal electrodes.
Thus, the coil device has a problem that the lead parts of the wire for winding and the terminal electrodes are prone to be connected insufficiently due to heat at the time of soldering for mounting the terminal electrodes on a circuit board, for example. In particular, the lead parts and the terminal electrodes are prone to be connected insufficiently when the lead parts and the terminal electrodes are connected close to a mounting surface for compactness of the device.
It is then discussed to connect the lead part of the wire for winding and the terminal electrode by such as laser welding and thermocompression at a temperature higher than that of solder. When the lead part of the wire for winding and the terminal electrode are connected by such as laser welding and thermocompression at a temperature higher than that of solder, however, a solder fillet is not formed at the lead connection part.
Thus, when a lead connection part is formed at one end in a longitudinal direction of the terminal electrode and a fillet forming part is formed at the other end, no fillet is formed on the lead connection part, and the terminal electrode is thereby affected by external force in the longitudinal direction due to solder formed on the fillet forming part. This external force may dislocate the terminal electrode and the coil device with respect to the circuit board for mounting. Also, a problem that strength between the terminal electrode and the circuit board for mounting is decreased is caused.
When the lead part of the wire for winding and the terminal electrode are connected by laser welding, a magnetic core may be damaged by a laser beam and its reflection during laser welding. It is conceivable that the magnetic core is damaged by breakage and crack due to thermal impact.
A coil device as shown in a publication (JP3171315 (U)) is also known. In this coil device, however, connection pieces for tying lead ends of a wire protrude outside the coil device at terminal electrodes. Then, the protruding portions may contact a device, such as a mounter, during transportation to a mounting machine, and its impact or stress may cause disconnection and break the core.
When a winding terminal without purpose for laser welding of a lead end is arranged near a magnetic core for compactness of the device and welded by laser as it is, the magnetic core may be also damaged by laser beam and its reflection during laser welding.